Kinim, Chapter Two, Mishnah One
You might call our mishnah “the pigeon that escaped.” It deals with a case where a single bird from an “unassigned ken”one in which it has not been determined which bird is a hatat and which is an olahescapes. The question is: what is the status of the bird that remains and the bird that escapes.
1) If from an unassigned pair of birds a single pigeon flew into the open air, or flew among birds that had been left to die, or if one [of the pair] died, then he must take a mate for the second one.
2) If it flew among birds that are to be offered up, it becomes invalid and it invalidates another bird as its counterpart [in the pair]; for the pigeon that flew away is invalid and invalidates another bird as its counterpart [in the pair].
Section one: In all of these cases, one bird leaves the unassigned ken. Since both birds were unassigned, all he has to do is take a new bird for the remaining bird and offer one as a hatat and one as an olah. However, if it had been a “determined ken,” one where we already knew which was which, he couldn’t sacrifice the remaining one unless he knew whether it was the hatat or the olah.
We should note that in all of these cases, nothing can be done with the bird that flew away, either because it is gone or dead, or because it became mixed up with other birds that must be left to die.
Section two: In this case, the bird that flew away gets mixed up with other birds from other undetermined kinim. It itself is invalid, and we can’t simply find a partner for it (a shidduch, if you will) because any bird we take might have been from one of the other birds that was to be offered up. It also invalidates one of the other birds that it joins. We shall explain this in the following mishnayot.